Winder motor control system



Nov. 1, 1955 G. E. SHAAD ET AL 2,722,639

WINDER MOTOR CONTROL SYSTEM Filed Nov. 22, 1952 3 Sheets-Sheet l Figl.

RHEOSTAT Inventors: George E. Shead,

Charles D.Beck, John C.Gr-eshem,

by @A H is Attor fiey.

Nov. 1, 1955 G. E. SHAAD ETAL 2,722,639

WINDER MOTOR CONTROL SYSTEM Filed Nov. 22, 1952 3 Sheets-Sheet 5 Fig.4.

BRAKING GENERATOR ARMATURE VOLTAGE 39b 39 d BRAKING GENERATOR CURRENT BOOS ER GEN ERATOR ARMATURE VOLTAGE FIELD CURRENT VOLTAGE CONTACTOR-Zl coufAcToR-zz CONTACTOR-ZZI cm wAcTow-z r Inventors: Geowr cge E. Shaad, Charles D. Beck, John C. GTeSham,

by T eirAttorrway.

United States Patent O WINDER MOTOR CONTROL SYSTEM George E. Shaad, Schenectady, Charles D. Beck, Scotia, and John C. Gresham, Schenectady,N. Y., assignors to General Electric Company, a corporation of New York Application November 22, 1952, Serial No. 322,074

Claims. (Cl. 318-6) This invention relates to control systems, more particularly to systems for controlling the winding of a length of material on a roll or the unwinding of a length of material from a roll, and it has for an object the provision of a simple, reliable and improved control system of this character.

Still more specifically, the invention relates to control systems for winder drives in which the winding and unwinding rolls are mechanically connected to a pair of dynamoelectric machines. One of these machines operates as a motor and the other operates as a braking generator to maintain tension in the length of material which is being wound or unwound. In numerous applications in which a winding or unwinding operation is involved, it is desired to maintain substantially constant tension in the material in order that the product shall be uniform. A further object of this invention is the provision of an improved and inexpensive winder control system for maintaining constant tension in the material which is being wound, unwound, or both.

Heretofore, there have been winder control systems in which constant tension was maintained in the material by varying the field excitation of the roll motor or braking generator by means of a roll diameter measuring rheostat. Systems of this character, although operable, leave much to be desired because the roll measuring rheostat is a source of trouble that results largely from its necessary location in close proximity to the roll and in such position that its actuating arm actually bears on the roll. The result is that a breakage in the material during high speed winding operations produces immediate loss of tension and a resultant sudden, almost explosive increase in roll diameter which usually wrecks the rheostat. Accordingly, a further object of this invention is the provision of an improved combination of progressively operable and repetitively operable electro responsive control means cooperating in a winder control system-whereby substantially constant tension is maintained in the material without the use of a roll diameter measuring rheostat having any mechanical connection to the roll.

A still further object of the invention is the provision of a constant tension winder control system in which electromagnetic means successively responsive to an electrical condition of the system are used to vary the excitation of the tension-producing dynamoelectric machine in appropriate steps relative to the decreasing diameter of the roll and auxiliary dynamoelectric control means serve to maintain the tension substantially'constant during each step.

In carrying the invention into effect in one form thereof, a dynamoelectric machine is connected to be supplied from an adjustable voltage generator for operation as a motor pulling on the material or as a braking generator driven by the material. Connected in circuit between the armatures of the dynamoelectric machine and the supply generator is the armature of an auxiliary generator which operates as a booster generator. For maintaining constant tension in the material a progressively variable resistor is connected in the field circuit of the dynamoelectric machine and a cooperating regulating means are provided which comprise a second auxiliary generator having a control field winding which is connected to be responsive to the armature current of the dynamoelectric machine and having its armature connected to the field of the first auxiliary generator together with electromagnetic means connected to be responsive to a predetermined voltage of one or the other of the auxiliary generators for varying the resistors in the field circuit of the dynamoelectric machine in a series of successive steps.

For a better and more complete understanding of the invention, reference should now be had to the following specification and to the accompanying drawings of which Fig. 1 is a simple, diagrammatical illustration of an embodiment of the invention; Fig. 2 is a modification; Fig. 3 is a chart of characteristic curves which facilitate an understanding of the operation of the system; and Fig. 4 is a chart of characteristic curves which serve to explain the operation of one of the elements of the system.

Referring now to the drawing, and particularly to Fig. l, a length of material 1 is being unwound from a roll 2 and is being rewound on another roll 3. Operation in the reverse direction with the material being unwound from roll 3 and rewound on roll 2 is also contemplated.

One of the applications for Which this invention is particularly well adapted is the rewinding of the mill roll of a paper-making machine on the finished roll. The full roll 2 may be considered to be the mill roll. Usually the edge of the mill roll is uneven and may be a number of times wider than the desired width of the finished product. Accordingly, the paper is unwound from the mill roll and after passing through edge trimmers and slitters which are not shown, the finished paper is rewound on the roll 3.

The roll 3 rests upon peripheral drive rolls 4 which are mechanically connected to the shaft of a direct current dynamoelectric machine 5 which operates as a motor to drive the rolls 4 and thus to wind the paper on the roll 3. The motor'5 is supplied from a suitable source such as the adjustable voltage generator 6 to the armature of which it is arranged to be connected through the normally open contacts 7b of a line contactor 7. Any suitable driving means such, for example, as an induction motor (not shown) may be used to drive the generator 6 at a suitable speed which is preferably substantially constant.

As shown, generator 6 is provided with a field winding 6a which is supplied from a suitable source of excitation such as represented by the excitation supply conductors 8 and 9. Similarly, the motor 5 is provided with a field winding 5a which is connected to the excitation supply conductors 3 and 9 so as to provide a constant motor field. A rheostat 10 is connected in circuit with the field winding 6a and when adjusted, it serves to adjust the voltage of the generator 6 and consequently, the speed of the motor 5 to desired values.

For the purpose of maintaining tension in the material during the winding operation, a direct current dynamoelectric machine 11 is electrically connected to the supply generator 6 and mechanically connected to be driven by the unwinding roll 2 so that it operates as a braking generator returning power to the supply generator. It is contemplated that for operation in the reverse direction with the material being unwound from the roll 3 and rewound on the roll 2 the dynamoelectric machine 11 'will operate as a motor and the machine 5 will operate as a braking generator.

In order to maintain stalled tension in the material when the drive is stopped, a booster generator 12 is provided.

Its armature is connected in circuit between the armatures of the supply generator 6 and the braking generator 11 so that it circulates current in the armatures of the braking generator and the winding motor when the voltage of the supply generator is reduced to a very low value or to zero. It is poled so that its voltage adds to the voltage of the braking generator. Thus, when the voltage of the supply generator is reduced to zero and the drive is stopped, the booster causes current to flow in the armatures of the braking generator 11 and winding motor 5 in the same direction as when it is running. Consequently, tension is maintained in the material when the drive is stopped.

This booster generator also cooperates with other elements of the system to regulate the tension in the material to a predetermined desired value during the winding operation. It is driven at a substantially constant speed by suitable means such as an induction motor (not shown) and preferably by the motor which drives the supply generator 6.

The braking generator is provided with a field winding 110 which is connected across the excitation supply conductors 8 and 9 so that the energization thereof may be progressively varied in steps as well as during each step in the following manner. In the circuit of this field winding is connected a progressively variable resistor 13 of which one portion 13a is connected in series with the field winding and a second portion 13b is connected in parallel therewith. Also connected in the field winding circuit is a regulating exciter 14 which is poled so that under most operating conditions its voltage adds to the voltage of the supply conductors as indicated by the polarity markings on the drawing. The field winding circuit of the braking generator is readily traced from the positive excitation supply conductor 8 through resistor portion 13a, conductor 15, field winding 11a, conductor 16 and through the armature of the regulating exciter 14 to the negative supply conductor 9. Conductors 15, 16 and 17 connect the resistor portion 13b in parallel with the field winding 11a. The booster generator is provided with a field winding 12a which is directly connected across the armature terminals of exciter 14 and consequently its armature voltage is in general a reproduction of the exciter voltage.

Preferably, the regulating exciter 14 is of the type which is disclosed in Patent 2,227,992Alexanderson et al. and which is known in the art as an amplidyne. It is provided with a pair of load circuit brushes 14a and 14b and a pair of short circuited brushes 14c and 14d which are mounted on an axis that is displaced 90 electrical degrees from the axis of the load circuit brushes. with a reference field winding 14:: which is connected to an external terminal 18a and to the slider 18b of a potentiometer 18 which is connected across the excitation supply conductors 8 and 9. It is also provided with an opposing control field winding 14 which is connected across the terminals of a resistor 19. This resistor is connected in series relationship with the armature of the braking generator 11. Thus, the opposing control field winding 14f is energized in response to the current flowing in the armature circuit.

Since the magnetization of the control field winding 14f opposes the magnetization of the reference field winding 14s, the amplidyne exciter 11 is thus responsive to the difference in excitation of the reference field winding and the control field winding to vary the excitation of the braking generator and the booster generator inversely with variations in the current in the armature circuit of the braking generator so as to maintain this current approximately constant at a value determined by the setting of the rheostat 18 in the circuit of the reference field winding. The tension in the material is approximately proportional to the current in the armature circuit of the braking generator, and since rheostat 18 determines the value of this current it is referred to as the tension rheostat.

The exciter is provided Cooperating with the amplidyne exciter 14 to maintain the current in the armature circuit of the braking generator constant is an electromagnetic relay 20 and a plurality of electromagnetically operated contactors 21, 22, 23 and 24 controlled thereby for varying the resistor 13 in the eld circuit of the braking generator. Time delay in the drop-out of these contactors is provided by means of capacitors 21d, 22d, 23d and 24d which are connected in parallel with coils 21a, 22a, 23a and 24a through suitable resistors. As shown, the relay 20 is provided with an operating coil 20a which is connected across the armature of the booster generator 12 so as to be responsive to its voltage. Since the armature voltage of the booster generator is a reproduction of the exciter voltage, connecting the coil 20a across the armature of the exciter is considered to be an equivalent alternative to connecting it across the armature of the booster. The relay 20 is also provided with an opposing coil which is connected in a resistor network which comprises the fixed resistors 25, 26, 27 and 28 and the variable potentiometer resistor 29. The resistors 25 and 26 are connected in series relationship to the excitation supply conductors 8 and 9. The circuit is traced from the supply conductor 8 through resistors 25 and 26 in series and through the normally closed contacts 30a of a sequencing time delay relay 30, and the normally open contacts 70 of line contactor 7 to the supply conductor 9. The time delay in the drop-out of relay 30 is illustrated as being produced by a capacitor 30g but it could be produced by other means such as a copper jacket. Likewise, the resistors 27, 28 and 29 are connected in series across the supply conductors 8 and 9. The circuit extends from conductor 8 through normally open contacts 7d of the line contactor, normally closed contacts 30b of the sequencing relay, resistors 27, 29 and 28 to the supply conductor 9. The coil 20b of the control relay is connected between the slider 29a of potentiometer resistor 29 and the junction point of resistors 25 and 26. The slider 29a of the potentiometer is mechanically connected with the slider 18a of the tension rheostat so that it is varied in proportion to adjustments of the tension control rheostat. This effectively counteracts any change in excitation of the main coil 20a which results from changes of the booster generator voltage that are produced by adjustment of the tension rheostat.

An understanding of the operation of relay 20 in response to successive variations in the voltage of the booster generator to a predetermined value will be facilitated by reference to the chart of characteristic curves of Fig. 3. Ordinates of these curves represent both the voltage of the booster generator and the ampere turns of coil 20a which is energized by the booster generator voltage. Abscissae of the curves represent adjustment of the tension rheostat from zero tension to tension. The relay is designed to pick up at a total value of ampere turns which is represented by the ordinate of curve 31 and to drop out at a total value of ampere turns which is represented by the ordinate of curve 32. The ideal relationship between booster voltage and position of the tension rheostat is represented by the broken line curve 33, and X represents the normal range of variation from the ideal due to the inherent difference between the pickup and drop-out values of relay 20. The relationship between position of the tension rheostat and the ampere turns of the opposing coil 20b is represented by the curve 34. Ordinates of the curve 35 for each position of the tension rheostat represent the values of booster voltage and also of ampere turns of the coil 20a at which the relay 20 will drop out. In other words, if for any position of the tension rheostat, the booster voltage and the ampere turns of coil 20a fall to the value represented by the corresponding ordinate of curve 35, the relay will drop out. An example will illustrate the foregoing. As shown, the pickup value of the relay is 3000 ampere turns and the drop-out value is 1000 ampere turns. At the 100% tension position of the tension rheostat, the booster voltage may 'be any value above 70% of full voltage and the ampere turns of coil 20a will be a proportional amount greater than 3500 ampere turns. The ampere turns of the opposing coil 2% will be 2500. Thus, the diflerence in ampere turns exceeds 1000 which is the drop-out value, and the relay accordingly remains picked up. However, if for this same position of the rheostat, the booster voltage falls to 70% of full value, the ampere turns of coil 20 will decrease to 3500. The difference in ampere turns of the two coils will be 1000 which is the drop-out value, and accordingly, the relay will drop out. A manually operated pushbutton type switch 35 and a contactor 36 controlled thereby serve when operated at the conclusion of a winding operation to restore the system to a reset condition preparatory to a new winding operation.

With the foregoing understanding of the elements and their organization in the system, the operation of the system will readily be understood from the following description: It is assumed that by closure of a suitable switch, not shown, the excitation supply conductors 8 and 9 are energized with voltage of the polarity illustrated on the drawing. In response to energization of its coil 20b, the relay 20 picks up and opens its normally closed contacts 200. The energizing circuit for the coil 20b is traced from the excitation supply conductor-8 through relatively low resistor 25, coil 20b, righthand portion of potentiometer 29 and relatively low resistor 28 to the negative supply conductor 9. Preparatory to starting, the manually operated type switch 37 is closed to complete an energizing circuit for the operating coil 7a of the line contactor 7. This energizing circuit is traced from the positive excitation supply conductor 8 through the contacts of the switch 37, coil 7a, to the negative supply conductor 9. In response to energization, the line contactor picks up and closes its normally open contacts 7b, 7c 7d, 7e, and 7 Contacts 7b and 7e in closing complete the armature circuits of the braking generator 11 and the winding motor 5 through the armature of the supply generator 6. Contacts 70 and 7d in closing complete connections of the network resistors 26 and 27 to the excitation supply conductors 9 and 8, respectively. At this point in the operation, the coil 20b of the relay 20 is no longer energized by the voltage across the conductors 8 and 9 but is now energized by the difference in voltage between the slider 29a and junction point of resistors 25 and 26 and its ampere turn relationship to the position of the tension rheostat is now represented by the characteristic curve 34 of Fig. 3.

In this figure the axis of the abscissa is shown as intersecting the ideal relationship line 33 at zero. Thus the ampere turns of curve 34 (coil 20b) will reverse at a point on the abscissa corresponding to the point at which the drop-out curve 35 intersects the curve 32 which corresponds to the actual drop-out ampere turns of relay 20. Curve 35 also reverses at the point on the abscissa line corresponding to the point at which the curve 34 intersects the line 32.

The reset push button switch 35' is now momentarily closed to complete an energizing circuit for the operating coil of the reset contactor 36. Responsively to energization, the contactor 36 picks up and closes its normally open contacts 36a, 36b, 36c and 36d. These contacts in closing complete energizing circuits for the operating coils of the contactors 21, 22, 23 and 24 which control the resistor in the field circuit of the braking generator. In response to energization, contactors 21 and 22 pick up and close their normally closed contacts 21a and 22a to short circuit both sections of the resistor section 13a. Similarly, contactors 23 and 24 pick up to open their normally closed contacts 23a and 24a to interrupt the parallel connection of the resistor portion 13b to the field winding 11a of the braking generator. Sincethe series resistor portion 13a is short circuited and the parallel resistor portion 13b is disconnected, the field winding 11a .6 of the braking generator is connected directly across the excitation supply conductors 8 and 9 in series relationship with the armature of the amplidyne exciter 14 and accordingly its excitation is at maximum strength. Contactors 21, 22, 23 and 24 in picking up complete sealing in circuits for their operating coils through contacts 30 30e, 30d and 300 respectively. The switch 35 may now be released and the reset contactor dropped out. Contacts 21c, 22c and 230 in closing complete additional holding circuits for contactors 22, 23 and 24 respectively.

The winding operation is initiated by rotating the slider 10a of the rheostat 10 in the field circuit of the supply generator in a clockwise direction to increase its excitation and voltage.

As the voltage of the supply generator 6 rises, the winding motor 5 is energized and its speed increases to a value corresponding to the final setting of the slider 10a. As a result, the finish roll 3 is accelerated to a corresponding speed and paper is unwound from the full roll 2 and delivered in the direction of the arrow to the winding roll 3. The rotation of the unwinding roll 2 drives the dynamoelectric machine 11 as a generator and in consequence, it generates a voltage which adds to the voltage of the booster generator 12 and supplies current to the supply generator 6 and to the winding motor 5. As the diameter of the unwinding roll decreases, the speed of the braking generator 11 increases, since the paper 1 is being Wound on the roll 3 at constant lineal speed. As a result of its increasing speed, the voltage of the braking generator increases initially at a rate which is somewhat greater than that represented by the slope of the portion of the curve 39 between the points 39a and 39b in the chart of characteristic curves illustrated in Fig. 4. This increasing voltage of the breaking generator tends to increase the current flowing in its armature circuit and consequently to increase the voltage drop across the resistor 19 thereby to increase the excitation of the opposing control field winding 14 of the exciter 14. This results in decreasing the voltage of the exciter and correspondingly decreasing the excitation of the field winding 12a of the booster generator which is supplied from the exciter.

As a result of its decreasing excitation, the voltage of the booster generator decreases as illustrated by the portion of the curve 40 between the points 40a and 40b of Fig. 4. The decreasing voltage of the exciter 14 has the further effect of decreasing the excitation of the field winding 11a of the braking generator. However, this decrease in excitation is not sufiicient completely to counteract the increasing speed of the braking generator and consequently, its voltage continues to rise in accordance with the portion of curve 39 between the points 39a and 39b which is somewhat less than the initial rate. The decrease in the field current of the braking generator for this portion of the operation is represented by the portion of the curve 41 between the points 41a and 41b.

The foregoing described operation continues until the voltage of the booster generator decreases to the pre determined value represented by the ordinate of the point 40b at which point the ampere turns of the coil 20a of relay 20 decrease to 3500 and (assuming the tension rheostat set at tension) the total ampere turns of the relay are decreased to 1000 and the relay drops out to close its normally closed contacts 20c.

Contacts 200 in closing complete an energizing circuit for the operating coil of the sequencing time delay relay 30. This energizing circuit is traced from the positive excitation supply conductor 8 through contacts 200, operating coil of relay 30 to the negative excitation supply conductor 9. Responsively to energization, contactor 30 picks up and opens its normally closed contacts 30a, 30b, 30c, 30d, 302, 30 and 30g. Contacts 30a and 30b in opening disconnect the network resistors 26 and 27 from the excitation supply structures so that the relay coil 2% is again connected directly across the excitation supply conductors and picks up the relay in response to the resulting high excitation. The resulting opening of contacts 20c interrupts the energizing circuit of the time delay relay 30 and it commences its timing out operation preparatory to dropping out. Contact 30 in opening interrupted the sealing-in circuit of the contactor 21. However, since contactor 21 is provided with time delay, it does not drop out immediately but begins timing out preparatory to dropping out. The opening of contacts 3%, 30d and 300 did not interrupt the energizing circuits for the operating coils of contactors 22, 23 and 24 since these coils remain sealed in through interlock contacts 210, 22c and 230.

Contactor 21 completes its timing out before relay 30 completes its timing out and, consequently, contactor 21 drops out and opens its normally open contacts 21a to insert the lefthand section of the resistor portion 13a in series with the field winding 11a of the braking generator. Contacts 21c in opening interrupt the sealing-in circuit of contactor 22 and it begins to time out preparatory to dropping out. However, before its timing out is completed the timing out of sequencing relay 30 is completed and it drops out to reclose its normally closed contacts 30c, 30a, 30a and 30 Contacts 30c, 30d and we in closing recomplete the sealing-in circuits of contactors 22, 23 and 24, and consequently these contactors remain picked up at this time. The closing of contacts 39 is unable to recomplete the energizing circuit of contactor 21 since this contactor is dropped out and its energizing circuit is opened at the contacts 21b.

The insertion of the lefthand section of resistor portion 13a in the field circuit of the braking generator causes the current in the field circuit to decrease abruptly as indicated by the portion of curve 41 between the points 4111 and 410. This abrupt decrease in field current produces a correspondingly abrupt decrease in the voltage of the braking generator which is illustrated in Fig. 4 by the vertical portion of curve 39 between points 3912 and 390. In response to the decrease of the braking generator voltage, the armature current begins to decrease also. However, the tendency of the armature current to decrease is counteracted by the rapid action of the regulator exciter 14 in response to the decreasing armature current to inversely increase its voltage and thus to inversely increase the excitation of the booster generator and the braking generator. This increase in excitation of the booster generator causes its voltage to increase sharply as illustrated by the vertical portion of the curve 40 between points 405 and 48c and thereby to counteract the decrease in armature current and restore it approximately to its original preset value. Similarly, the increase in the excitation of the braking generator counteracts further decrease in its voltage.

As the winding operation continues, the voltage of the braking generator again increases in response to the decrease in diameter of the roll and the regulator exciter responds to the resulting increase in armature current to effect a corresponding decrease in the booster generator voltage. This continues until the voltage of the booster generator decreases to the predetermined value represented by the ordinate at point 40d of curve 40. At this value of booster voltage, the relay 20 again drops out and the previously described operation of the sequencing relay Si) is repeated. This time, however, the contactor 22 is dropped out to insert a second sec tion of resistance in the field circuit of the braking generator and the system again operates in the manner previously described in connection with the operation of contactor 21.

As the winding operation continues, the booster generator voltage successively increases and decreases as explained in the foregoing When it decreases to the value represented by the ordinate of point 402, the contactor 23 drops out and closes its contacts 23:: to connect the resistor portion 13b in parallel with the field winding of the braking generator thereby to effect a further decrease in its excitation. Similarly, when the contactor 24 drops out it closes its contacts 24a to short circuit the lefthand section of the parallel resistor portion 13b thereby still further to weaken the field of the braking generator.

From the foregoing it is seen that the net effect of the operation of the system is to progressively insert resistance in the field of the braking generator in proportion to the decrease in diameter of the unwinding roll and to maintain the armature current substantially constant as the unwinding operation proceeds thereby to maintain the tension in the material substantially constant. Thus in Fig. 4 the average of the curve marked Braking Generator Field Current would represent at a given linear sheet speed the decrease in size of the reel. The inverse of this curve would then represent the increase in speed of the reel.

In the modification illustrated in Fig. 2, the armatures of the winder motor 5, the supply generator 6, the braking generator 11, and the booster generator 12 are connected in the same manner as in Fig. l.

The reference field winding 14e of the amplidyne exciter 14 is connected across the excitation supply conductors 8 and 9 with the tension rheostat 1 5 connected in series relationship. Its opposing control field winding 14] is connected across two resistors of which one is the resistor 19 and the other is a second resistor 42 connected in series relationship between resistor 19 and the armature of the winder motor 5.

In this modification, the booster generator 12 is provided with the usual main field winding 12a and with an additional field winding 12b which, under most conditions of operation, opposes the main field winding. A rheostat 43 is connected in series relationship with a fixed resistor 44 across the excitation supply conductors 8 and 9. The additional booster field winding 12b is connected between the slider 43a and the supply conductor 9. As shown, the slider of the rheostat 43 is mechanically connected with the slider of the tension rheostat 13 so that adjustment of the tension rheostat produces a simultaneous and proportional change in the excitation of the booster generator.

The resistance element 45 of a motor operated rheostat is connected in series relationship with the field winding 11a of the braking generator, and its driving motor 46 is connected across the load circuit armature terminals of the amplidyne exciter. In series relation ship with the armature of the rheostat motor 46 is connected a blocking rectifier 47. This rectifier is preferably of the selenium disk type and is provided with a number of disks such that its non-linear resistance characteristic prevents sufficient current from flowing through the armature of the motor 46 to effect rotation until the voltage across the resistor exceeds a predetermined value, e. g. 8 volts.

The operation of the system is as follows: The ten sion adjusting rheostat 18 is adjusted to a position corresponding to the desired value of tension in the material. Subsequently the system is started from rest and brought up to speed in the manner which is already described in connection with Fig. l. The adjustment of the tension rheostat results in a correspondins adjustment of the booster generator field rheostat such that the booster generator supplies to the armature circuit of the braking generator a voltage approximately equal to the RI drop in the power circuit which includes the armatures of the winding motor 5 and the braking generator 11. Under these conditions, the regulating amplidyne generates either zero voltage or a low voltage, i. e. 2 or 3 volts which is positive at the brush 14a. in either event, zero voltage is supplied to the motor since the rectifier is poled to block current flow in the armature circuit of the rheostat drive motor when the amplidyne voltage is positive at brush 14a. At-the beginning of the winding operation, the slider of the motor operated rheostat 45 is in a position in which the resulting excitation of the braking generator produces a voltage which, added to the voltage of the booster generator, equals the voltage of the supply generator.

As the material unwinds from the unwinding roll 2, the roll diameter decreases and the speed of the braking generator increases correspondingly. This increases the voltage of the braking generator which in turn tends to increase the current in the armature circuit. The excitation of the control field winding 14] of the amplidyne exciter, which is connected to be responsive to the armature current of the braking generator, is correspondingly increasedthereby causing theexcitation of the amplidyne to pass through zero (if it is positive at the brush 14a) and generate an increasing voltage of reverse polarity.

As a result, the net excitation of the booster generator is weakened so that its voltage is decreased to maintain constant current in the armature circuit of the braking generator. The reverse polarity voltage of the amplidyne 14 continues to increase as the speed of the braking generator increases until at a predetermined value of negative voltage of the amplidyne, the rectifier 47 passes current and energizes the rheostat motor 46.

Responsively to energization, the rheostat motor runs and moves the slider 45a in a direction to insert a block of resistance in the field circuit of the brak'ing generator. This causes the voltage of the braking generator suddenly to decrease which in turn causes the current in its armature circuit to decrease. The decreasing armature current weakens the net excitation of the amplidyne thereby causing its reverse polarityvoltage to decrease to zero. This weakens the net excitation of the opposing field winding 12a ofthe booster generator. and correspondingly increases its armature voltage to restore thecurrent in the armature circuit of the braking generator approximately to its former value.

The decrease of the amplidyne voltage below the predetermined value necessary to establish current flow through the rectifier 47 and armature of the rheostat motor 46 deenergizes and stops the rheostat motor.

As the winding operation continues, the foregoing described operation is repeated. Thus the modification of Fig. 2 operates in a manner somewhat similar to that of the Fig. 1 modification to insert resistance in the field circuit of the brakingv generator in a series of .successive steps and generally in proportion to the decrease in roll diameter of the unwinding roll, and it also operates to maintain the current in the armature circuit approximately constant thereby to maintain substantially constant tension in the material.

Although in accordance with the provisions of the patent statutes this invention is described as embodied in concrete form andthe principle of the invention has been described together with the best manner in which it is now contemplated applying that principle, it will be understood that the description is merely illustrative and that alterations and modifications will readily occur to persons skilled in the art without departing from the true spirit of the invention or from the scope of the annexed claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A winder control system comprising in combination an adjustable voltage supply generator, a pair of dynamoelectric machines having their armatures connected to said generator to provide operation of one of said machines as a winding roll driving motor and operation of the other as an unwinding roll braking generator and regulating means for maintaining the armature current in said other dynamoelectric machine approximately constant comprising a booster generator having an armature in series with the armature ofthe braking generator and provided with an auxiliary excit'er excited in response to the current in said armature circuit for generating va predetermined control voltage each time the current exceeds a predetermined value, a progressively variable resistor connected in the field winding circuit of said other machine and electro-responsive means'conn'ected to be successively responsive to said predetermined control voltage for progressively varying said resistorto weaken the excitation of said other machine in successive steps as its speed increases.

2. A Winder control system comprising in combination an adjustable voltage main supply generator, a pair of dynamoelectric machines each having a field winding and one of said machines having itsa'rmature connected to be supplied from said generator for operation as a'winding roll driving motor and the other having its armature connected to said generator for operation as anunwinding roll braking generator, a first auxiliary generator having its armature connected in circuit between the armature of said main generator and the armature of said "other dynamoelectric machine, a progressively variable resistor connected in circuit with the field Winding of said other dynamoelectric machine, and regulating means for maintaining the current in the armature circuit of said other dynamoelectric machine approximately constant comprising a second auxiliary generator having a field Winding connectedto be responsive to the current in said armature circuit and having its armature connected to supply excitation to the field Winding of said first auxiliary generator to cause its voltage to vary inversely with variations in the armature current of said first auxiliary generator, and electro-responsive means connected to be successively responsive to a predetermined voltage of one of said auxiliary generators for progressively varying said resistor.

3. A system for controlling the unwinding of a length of material from a roll and 'rewinding it on a winding roll comprising in combination an adjustable voltage main supply generator, a winding roll motor supplied from said generator, means for producing tension in the material being unwound comprising a braking generator driven by the unwinding-roll and having its armature electrically connected to said supply generator, a first auxiliary generator having its armature connected in circuit between the armature of said main generator and the armature of said braking generator, a progressively variable resistor connected in circuit with the field winding of said braking generator, regulating means for maintaining the current in the armature circuit of said braking generator approximately constant comprising a second auxiliary generator having a reference field winding circuit and an opposing control field winding connected to be responsive to the current in said armature circuit and having its armature connected to supply excitation to the field winding of said first auxiliary generator to cause its voltage to vary inversely with variations in the armature current of said first auxiliary generator, means including an electro-responsive device connected to be successively responsive to a predetermined voltage of one of said auxiliary generators for progressively varying said resistor to reduce the excitation of said braking generator as its speed increases in steps and means for adjusting the tension in said material to a desired value comprising a rheostat connected in said reference field Winding circuit.

4. A winder control system comprising in combination a source of direct voltage, a'pair of dynamoelectric machines each having a field winding and one of said machines having its armature supplied from said source for operation as a winding roll motor, and the other having its armature connected to said source for operation as a breaking generator, a progressively'variable resistor in the field circuit of said breaking generator, a booster generator having its armature connected between said source and the armature of said braking generator, and regulating means for maintaining the current in the armature circuit of said braking generator approximately constant comprising electro-responsive means connected to be successively responsive to a predetermined voltage across said booster generator for progressively varying the resistance in the field circuit of said braking generator, and an exciter responsive to variations in the current in said armature circuit of the braking generator for inversely varying the excitation of both said booster generator and said braking generator.

5. A winder control system comprising in combination, a source of adjustable direct voltage, a pair of dynamoelectric machines each having a field winding and one of said machines having its armature supplied from said source for operation as a winding roll motor, and the other having its armature connected to said source for operation as a braking generator, a booster generator having its armature connected in a circuit between said source and the armature of a first of said dynamoelectric machines, a variable resistor connected to the field winding of said first dynamoelectric machine, and regulating means for maintaining the current in the armature circuit of said first dynamoelectric machine approximately constant, comprising an exciter responsive to the current in said armature circuit for varying the excitation of said booster generator and the excitation of said first dynamoelectric machine, and an electroresponsive device connected to be responsive to the voltage across said booster generator and a plurality of switching devices sequentially responsive to successive operations of said electro-responsive device for varying said resistor to vary the excitation of said first dynamoelectric machine.

6. A system for controlling the winding of a length of material on a roll comprising in combination an adjustable voltage supply generator, a pair of dynamoelectric machines each provided with a field winding and each having its armature connected to said generator to provide for operation of said machines as a Winding roll motor and as braking generator driven by the material, a booster generator having its armature connected in a circuit between the armature of said supply generator and the armature of a first of said machines, a variable resistor electrically connected with the field winding of said first machine, and regulating means for maintaining the current in the armature circuit of said first dynamoelectric machine approximately constant to maintain the winding tension substantially constant comprising an exciter having a control field Winding connected to be responsive to the current in said armature circuit and having its armature connected in the field winding circuit of said first machine and to the field winding of said booster generator, a relay having an operating coil connected to be responsive to the voltage across said booster generator and a plurality of contactors connected to be sequentially responsive to successive operations of said relay for varying said resistor in successive steps to vary the excitation of said first machine.

7. A system for controlling the winding of a length of material on a roll comprising in combination an adjustable voltage supply generator, a pair of dynamoelectric machines having their armatures connected to said generator for operation of one of said machines as a winding roll motor and operation of the other as a braking generator, a booster generator having its armature connected in circuit between the armature of said supply generator and the armature of a first of said machines, regulating means for maintaining the current in the armature circuit of said first machine substantially constant to maintain substantially constant tension in the material being wound comprising an exciter having a reference field winding and having an opposing control field winding connected to be responsive to the current in said armature circuit and having its armature connected in the field circuit of said first machine and to the field winding of said booster generator, a variable resistor electrically connected in the field winding circuit of said first machine, a relay having an operating coil connected to be responsive to the voltage across said booster generator and a plurality of contactors sequentially responsive to successive operations of said relay for varying said resistor in successive steps to vary the excitation of said first machine, a tension ad justing rheostat connected in circuit with one of said exciter field windings, a rheostat in circuit with an operating coil of said relay for varying its ampere turns and a common mechanical connection between said rheostats for varying the setting of said relay simultaneously with and in proportion to changes in tension adjustments.

8. A winder control system comprising in combination an adjustable voltage supply generator, a pair of dynamoelectric machines having their armatures connected to said generator to provide for operation of one of said machines as a motor and the other as a braking generator, a booster generator having its armature connected in a circuit between the armatures of said supply generator and a first of said machines, a variable resistor connected in the field winding circuit of said first machine, regulating means for maintaining the current in the armature circuit of said first machine substantially constant comprising an exciter having a control field winding connected to be responsive to the current in said armature circuit and having its armature connected in said field winding circuit and to the field winding of said booster generator, a relay having a coil connected to be responsive to a decrease of the voltage of said booster generator to a predetermined value for effecting operation of said relay from a first operating position to a second operating position, a second relay operable to a first position in response to said operation of said voltage responsive relay to restore said voltage responsive relay to its said first position and operable to a second position in response to said restoration of said first relay after a predetermined interval of time, and a plurality of contactors operable in response to successive operations of said second relay for varying said resistor in steps.

9. A winder control system comprising in combination, an adjustable voltage supply generator, a pair of dynamoelectric machines having their armatures connected to said generator to provide for operation of one of said machines as a motor and operation of the other as a braking generator, a booster generator having its armature connected in a circuit between the armatures of a first of said dynamoelectric machines, regulating means for maintaining the current in the armature circuit of said first dynamoelectric machine substantially constant comprising an exciter having a reference field winding and having an opposing control field winding connected to be responsive to the current in said armature circuit and having its armature connected in the field winding circuit of said first machine and to the field winding of said booster generator, a variable resistor connected in the field circuit of said first machine, a source of constant voltage, a relay having a first coil connected to be energized from said source and having a second coil connected to be responsive to the voltage of said booster generator for effecting successive operations of said relay in response to successive decreases of said booster voltage to a predetermined value and a plurality of contactors connected to be sequentially responsive to said successive operations of said relay for varying said resistor in steps to vary the excitation of said first machine, a tension adjusting rheostat connected in circuit with said reference field winding, a second rheostat connected in circuit with said first coil and a common mechanical connection between said rheostats for varying the response setting of said relay simultaneously with and in proportion to changes in tension adjustments.

10. A winder control system comprising in combination, an adjustable voltage supply generator, a pair of dynarnoelectric machines, one of said machines having its armature supplied from said generator for operation as a motor and the other of said machines having its armature connected to said generator for operation as a braking generator, a booster generator having its armature connected in a circuit between the armatures of said supply generator and a first of said machines, a resistor having a portion connected in series with the field winding of said first machine, and a second portion connected in parallel with said field winding and regulating means for maintaining the current in said series circuit substantially constant comprising an exciter having a control field winding connected to be responsive to the current in the armature circuit of said first machine and having its armature connected to the field winding of said booster 14 generator and in circuit with the field winding of said first machine, and a relay responsive to the voltage of said booster generator and a plurality of contactors sequentially responsive to successive operations of said relay for varying said portions of said resistor in steps.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,353 Umansky May 4, 1937 1,920,897 Shoults Aug. 1, 1933 2,024,708 Staege Dec. 17, 1935 2,165,127 Carnegie July 4, 1939 2,333,978 Bowman Nov. 9, 1943 2,437,973 Schmitz Mar. 16, 1948 2,468,557 Huston Apr. 25, 1949 

